Weather Service Report

FXUS66 KPQR 011031

Area Forecast Discussion
National Weather Service Portland OR 
331 AM PDT Fri Jul  1 2016

.SYNOPSIS...A persistent weather pattern will result in coastal low
clouds spreading inland each night with clearing in the afternoons. A
couple of weak upper level disturbances will produce light drizzle or
rain along the coast and northern areas at times. Temperatures will
remain near early July normals today and Saturday, then trend a
little cooler early next week as a flat upper level trough settles
into western Canada and Washington.


.SHORT TERM...(Today through Sunday Night)...Typical early summer
onshore flow pattern persists today, with stratus gathering along the
Washington and northern Oregon coasts. The moist onshore flow,
powered by gradients still about +7 mb from KAST-KPDT, is also
causing some low clouds to develop in the foothills of the S WA
Cascades and Mount Hood. Expect low clouds to continue to fill in
this morning north of a Tillamook to Mt Jefferson line, though a few
gaps will probably remain by sunrise. Present expectation is that
areas south of Salem will stay mainly clear this morning due to a
greater northerly component to the pressure gradients cutting off the
source of moisture in the boundary layer. For the north, low clouds
should clear back to the coast around midday, with plenty of
afternoon sunshine inland. High temperatures today should overall be
very similar to yesterday and close to seasonal norms...generally
close to 80 for most inland valleys.

Persistence pattern continues into Saturday, with perhaps a little
more low cloud coverage due to a weak shortwave developing offshore
and shown by the 00z GFS/ECMWF to move across WA Sat AM. The
shortwave may encourage a little drizzle to fall out of the stratus,
mainly in our northern coastal and higher terrain zones. Slightly
more widespread and persistent clouds may cause temps to be a couple
degrees cooler than today.

The gradual cooling trend looks to continue into Sunday as a more
significant shortwave and associated cold front move across WA and NW
Oregon. Sunday morning will probably have the best chance of drizzle
or light rain out of the next three, with fairly widespread low
clouds extending inland all the way down to Eugene. Again the best
chance for -DZ/-RA will be along the north coast and higher terrain,
but a couple spits of -DZ/-RA cannot be ruled out for the PDX Metro
Sunday morning, especially closer to the foothills. Stubborn low
clouds should give way to some afternoon sunshine, but a cooler air
mass and fewer hours of sunny skies will probably knock temperatures
down a few more degrees...perhaps even a couple degrees below normal
in some areas.Weagle

.LONG TERM...(Monday/Independence Day through Thursday)...Slow
transition to below normal temps is likely to continue Mon/Tue, with
a longwave trough axis settling into the Pac NW. Ironically, the
upper trough may actually help the chances for clear skies in the low
levels the evening of the 4th, even along the coast, due to cooler
air aloft weakening the marine inversion...possibly enough to scatter
out the coastal stratus. 00z GFS/ECMWF do bring a stronger shortwave
onshore Mon afternoon/evening, which could produce some clouds itself
and perhaps a stray shower or two north of Portland. Reinforcing shot
of cool air behind this system will likely keep temps below normal
into mid-week. Model and ensemble agreement then falls apart Thu/Fri,
with some members suggesting a ridge will try to build northward from
California. However the majority opinion of the models/ensembles keep
the Pac NW under somewhat of a trough for near to below normal temps
for the rest of the week. 00z ECMWF operational run even brings a
strong enough frontal system onshore to bring a threat for rain
Thursday, though we discounted this solution for the time being, as
it is a bit of an outlier and climatological PoPs are very low this
time of year anyway.  Weagle


.AVIATION...VFR conditions prevailing today and evening with
increasing chances for MVFR later tonight and Sat. Expected to see 
some MVFR CIGS ranging from 1500 and 2500 feet extending from the
Cascade Foothills north of KSLE to the coast this morning. KAST
area may occasionally see MVFR cigs mixed with VFR conditions
through early afternoon while the remainder of the coast should
remain VFR. More widespread MVFR CIGS return this evening the
spread inland overnight as a weak upper trough shifts across the

KPDX AND APPROACHES...VFR conditions today through most of
tonight. However there is a good chance for some MVFR stratus
around 2000 feet through 16Z. MVFR CIGS likely to return after 08Z
Sat.  mh


.MARINE...Typical summer-time pattern continues with high
pressure over the WA and OR waters and a thermal low over
California. A weak front to move across the waters today and
tonight will interrupt this pattern which will weaken the northerly
winds today and Saturday. Next chance for advisory winds will
probably be on Sunday afternoon and evening as high pressure
strengthens over the waters. Northerly winds looks to continue
into next week.

Seas are a mix of steep wind waves and small fresh well, although
a small background long-period south swell also occasionally
becomes noticeable as well. The seas will generally hover between
3 and 5 ft today with larger swell tonight and Saturday with seas 
building seas up to around 5 to 7 ft through early next week.
Seas fall back down to 4 to 5 ft by midweek next week.





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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. The area is
commonly referred to as the forecast area.

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